If Thailand's suddenly lethal political tsunami results in a military coup, it wouldn't be surprising. The military has taken over 18 times since the country became a constitutional monarchy in 1932. Bangkok's colour-coded street activists – the Reds, Yellows and Blues – recall the rival chariot-racing factions of ancient Rome's Circus Maximus. Except in these troubled times, Thailand makes even Italy look like a model of democratic stability.

Abhisit Vejjajiva is Thailand's third prime minister in almost as many months and lacks both electoral legitimacy and grassroots credibility. An Eton- and Oxford-educated Geordie (he was brought up in Newcastle-upon-Tyne), Abhisit always seemed an odd choice for national crisis manager, ever since being picked in a backroom deal in December. Now that he has invited soldiers on to the streets, he may encounter difficulty persuading them to go back to barracks.

In Thailand the army is rarely far away. The military has not convincingly relinquished control since trashing the elected government of Thaksin Shinawatra in a September 2006 coup. All Thailand's current political travails stem from that moment.

As ever, the generals claimed to be acting in the nation's best interests. As usual, they bit off more than they could chew. In reality, theirs was a sectional concern; and its impact was divisive, not unifying. The temporary, deceptive calm they imposed was quickly overwhelmed by tidal waves of popular anger, with the left, right and centre, the middle and lower classes, the well-off and the poor taking tumultuous turns to vent their spleen on whoever was nominally in charge.

Thaksin the exiled billionaire remains a controversial and central figure. His family's business dealings provoked numerous allegations of corruption while he was in power. His often tacky, populist politics and cash giveaways to the rural poor in the north and east brought accusations of vote-buying. His handling of the long-simmering Muslim insurgency in the south was at times clumsy and provocative.

But Thaksin did possess one virtue: he was elected, and then re-elected, by democratic margins big enough to outweigh the usual opposition claims of fraud and malpractice. He had a legitimate base. He held the country together, a feat now more easily appreciated as it tears itself apart. And he briefly enhanced Thailand's international standing, in sharp contrast to the weekend's national humiliation that saw the leaders of Asia scrambling hastily for the exit as pro-Thaksin demonstrators stormed their regional summit meeting in the beach resort of Pattaya.

The normally soft-spoken Abhisit was beside himself with rage and declared a state of emergency in the capital. "On the country's loss today, whoever declares this as victory, I will treat them as national enemies. I will do whatever I can to make sure these people cannot stay above the law," he said.

This did not sound like a man ready to pursue the process of national reconciliation that Thailand so badly needs after three bruising years. What it did sound like was a man who may need the army, and the paramilitary Blues faction, if he is to hold on to power.

Whether Thaksin could do any better at bringing the country together and restoring democratic and judicial standards is also far from clear. He appears to have played a significant role from afar in fomenting the latest crisis, which followed last autumn's resurgence of his main rivals, the People's Alliance for Democracy, aka the Yellows, and December's banning of the pro-Thaksin People Power Party, aka the Reds.

It was Thaksin who set a deadline last week, ignored by the government, for the calling of fresh elections. It is Thaksin who has been urging Thais to pursue a "peaceful revolution", vowing yesterday that there could no peace without justice. And it is Thaksin who has carefully refused to rule out a return to his native soil, despite extant warrants for his arrest. "If our people in Bangkok and all the provinces unite ... I think this time we can change the country," he said.

The prospect of the former prime minister's return to power gladdens the hearts of half the country and utterly appals the other half. It is this possibility that could lead, more than any other single factor, to another military coup to forestall him.

But while Thailand is a land of rage, it is also the land of the deal. The crisis is costing it dear, exacerbated by global recession. The IMF says the economy may contract by 4% this year. The markets are down, tourism is slumping and business is bad. As in the past, a national accommodation is possible; as of now, it is plainly in the common interest. Thailand's political tsunami may subside as quickly as it erupted – but only if the generals can be kept locked in their box.